Help Please..DPC ISSUES since new GFX card

Discussion in 'General Hardware' started by BetA, Jul 31, 2010.

  1. BetA

    BetA Ancient Guru

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    Deferred Procedure Call

    Background information: Why drop-outs occur

    Processing of streaming data in real-time is a very challenging task for Windows based applications and device drivers. This is because by design Windows is not a real-time operating system. There is no guarantee that certain (periodic) actions can be executed in a timely manner.

    Audio or video data streams transferred from or to an external device are typically handled by a kernel-mode device driver. Data processing in such device drivers is interrupt-driven. Typically, the external hardware periodically issues interrupts to request the driver to transfer the next block of data. In Windows NT based systems (Windows 2000 and better) there is a specific interrupt handling mechanism. A device driver cannot process data immediately in its interrupt routine. It has to schedule a Deferred Procedure Call (DPC) which basically is a callback routine that will be called by the operating system as soon as possible. Any data transfer performed by the device driver takes place in the context of this callback routine, named DPC for short.

    The operating system maintains DPCs scheduled by device drivers in a queue. There is one DPC queue per CPU available in the system. At certain points the kernel checks the DPC queue and if no interrupt is to be processed and no DPC is currently running the first DPC will be un-queued and executed. DPC queue processing happens before the dispatcher selects a thread and assigns the CPU to it. So, a Deferred Procedure Call has a higher priority than any thread in the system.

    Note that the Deferred Procedure Call concept exists in kernel mode only. Any user-mode code (Windows applications) runs in the context of a thread. Threads are managed and scheduled for execution by the dispatcher.

    While there is a pre-emptive multitasking for threads, DPCs are executed sequentially according to the first in, first out nature of a DPC queue. Thus, a sort of cooperative multitasking scheme exists for Deferred Procedure Calls. If any DPC runs for an excessive amount of time then other DPCs will be delayed by that amount of time. Consequently, the latency of a particular DPC is defined as the sum of the execution time of all DPCs queued in front of that DPC. In order to achieve reasonable DPC latencies, in the Windows Device Driver Kit (DDK) documentation Microsoft recommends to return from a DPC routine as quick as possible. Any lengthy operation and specifically loops that wait for a hardware state change (polling) are strongly discouraged.

    Unfortunately, many existing device drivers do not conform to this advice. Such drivers spend an excessive amount of time in their DPC routines, causing an exceptional large latency for any other driver's DPCs. For a device driver that handles data streams in real-time it is crucial that a DPC scheduled from its interrupt routine is executed before the hardware issues the next interrupt. If the DPC is delayed and runs after the next interrupt occurred, typically a hardware buffer overrun occurs and the flow of data is interrupted. A drop-out occurs.

    If any kernel-mode device driver in your Windows system is implemented improperly and causes excessive latencies of Deferred Procedure Calls (DPCs) then probably drop-outs will occur when you use real-time audio or video streaming applications.

    taken from here:
    http://www.thesycon.de/deu/latency_check.shtml#background

    theres also more info, and if thats not enough, theres still google ;)
     
  2. IcE

    IcE Don Snow Staff Member

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    So it's how Windows talks to the hardware. But really, I've never heard of too much DPC latency being an issue. It sounds like your card is just defective. Try running it at stock.
     
  3. BetA

    BetA Ancient Guru

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    lol..
    if you did read the whole post you would know that i tried everything...
    it has nothing to to with OC cause it happens when the GPU is downclocking in 2d mode..@ 52 mhz ....

    As you see in the Pics, its an issue with the drivers from nvidia...
    if the gpu is on load everything is perfect..

    and im not the only one who had such issues..just google..

    greetz and gn8, beta
     
  4. cliffgamerz

    cliffgamerz Master Guru

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  5. morbias

    morbias Don TazeMeBro Staff Member

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    Try disabling HPET (High Precision Event Timer) in your BIOS.
     
  6. CoreyPL

    CoreyPL Master Guru

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    To disable nVidia Power Management:
    go to NVIDIA Control Panel with advanced mode -> Manage 3D Settings -> Change power management mode in global settings from adaptive to "Prefer maximum performance"

    I've made the translation from Polish, so it might not be accurate, but you should find the proper option without problem.

    It should stop the downclocking, but it will increase power consumption.

    I hope this help just until they finally fix it.

    EDIT:
    Have you tried disabling Nvidia Audio in device manager, instead uninstalling it?

    Before installing drivers you can also try to unpack them manually first using 7zip, and then deleting "hdaudio_1.0.15.0_xp_vista_win7.exe" file. Then you run setup.exe manually. I don't know if it will post an error or not - I have not tested it.

    EDIT II:
    I've triend DPC Latency testing on my system, but with GeForce G210, as my new and shiny GTX460 is on RMA because of damaged HDMI port. Using the same drivers as you. My latency is close to 500us when card is downclocked to 130MHz (lowest clock for G210), and maybe 250us when on full clock. So even with older cards there are fluctuations when the card is downclocked.

    I will check it again when I get my GTX460 back.
     
    Last edited: Jul 31, 2010
  7. BetA

    BetA Ancient Guru

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    hy, i tried power savings in Nvidia NCP..but whenb i set it on max performance instead of adaptive, its kinda the same..its downclocking no matter what..
    because this feature only applys to 3d aplications..
    so when a 3d app is running it will not downclock, but in desktop mode this option is useless...

    i also have tried disabling nvidia hd audi, i tried to uninstall it but windows allways reinstalling it ion reboot, but hd audio is not the problem...i chekked that..

    @ morbias

    *Try disabling HPET (High Precision Event Timer) in your BIOS.*

    i allready did that was the second thing that came to my mind..
    i testet 4 times with on and off...and even reinstalled win 7 CLEAN like i said before..

    greetz Beta
     
  8. BetA

    BetA Ancient Guru

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    Does someone know how i can DISABLE the 2D mode?And Force 3D mode..it doesnt work with afterburner...2d mode musst be disabled in the bios or something.
    also setting alwyas power in NCP doesnt work ether, because its only ment for ingame..
    so i can test something, and get rid of these spikes?
    Nibitor doesnt work :(

    greetz Beta
     
    Last edited: Aug 1, 2010
  9. TheHunter

    TheHunter Banned

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  10. BetA

    BetA Ancient Guru

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    jup, i did but still waiting for replys..
    nvidia is slow as hell...their support kinda sucks, ┬┤dunno about gigabyte, was in the geramn forum, but couldnt even post lol..or start a new thread..so i will try your link later on..
    greetz Beta
     

  11. TheHunter

    TheHunter Banned

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    yea make an account/passport there, and question in the second link.

    You will be in touch directly with GigaByte support team. Sometimes they're a little stubborn, i had to ask the same question twice lol.. but if you post enough data, maybe this thread too, it will be fixed in no time :nerd:
     
  12. BetA

    BetA Ancient Guru

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    ok, thx for the advice, and i guess i have enough proof and research to proof theres something wrong with the bios or the drivers ;)
    will do this when i get home, now i go over to a friends house and have some cold beers ;)
    hehe....cya Later Hunter......have a nice day mate...

    greetz Beta
     
  13. Mark121

    Mark121 Member Guru

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    The switching from 2d clocks 3d clocks is mostly likely the problem my friend how has Clevo M860TU
    had similar issue with switching clocks the effects where popping sounds static/drop outs.
    Nvidia released a beta driver for laptops that fixed his issue.

    I had similar problem but in my HTPC the culprit was the wireless card.
    If you have a wireless card disable it or remove it and see if it improves.
    good luck.
     
  14. naike

    naike Ancient Guru

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    nvm someone said it already
     
  15. BetA

    BetA Ancient Guru

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    @ Mark..

    i allready stated that it is Nvidias driver and 2d mode...i dont even have an wireless..
    i allready testet every single hardware..

    If u read the Thread again u will see taht it is 100% Nvidias fault...
     

  16. CoreyPL

    CoreyPL Master Guru

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    Have you tried to setting all the frequencies (RAM, PCI-E etc.) manually? Maybe with OC involved system is making some auto adjustments that screw up the latency?

    Also have you tried different BIOSes for your P5Q? What exact model do you have? I'm using BIOS modified by Ket - he put some new things like memory table, fresh RAID ROMs etc. Maybe this BIOS will do better job with your card?

    EDIT:
    Maybe try to put your card in the x8 slot - I know it's a little stretch solution, but at this point I have nothing more to suggest...
     
    Last edited: Aug 2, 2010
  17. BetA

    BetA Ancient Guru

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    i didnt OC the card at first and it had dpc issues..its the same with or without OC..

    i have the latest KET mbios just like u!!^^ causse i know there are good..

    and i dont have another pci e port..its an sinlge pci e mobo..(asus p5q)

    i even tried new win install and had everything at stock settings..

    im gonna wait till Nvidia makes an statement, wich i dont believe...

    greetz, over and out
     
    Last edited: Aug 2, 2010
  18. CoreyPL

    CoreyPL Master Guru

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    I've meant CPU OC, when you set FSB, RAM, PCi-E freq. Try to set them all to manual, don't leave anything on auto. Probably it won't change a thing, but maybe worth a try?

    I've also seen some people setting the PCI-E freq to 101MHz instead of default 100MHz when they OC the CPU. They claim that this increases stability. So maybe it will reduce latency?
     
  19. BetA

    BetA Ancient Guru

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    allready tried that...when i installed win 7 new...every thing was at stcok settings, even underclocked lol..pci e settings 100 or 101 or 102 didnt change a thing ;) i wouldnt go higher on the pci e mhz...

    anyway thx for the advices...

    greetz Beta
     
  20. sykozis

    sykozis Ancient Guru

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    Has anyone stopped to consider the fact that the GTX460 is a brand new card??? Or the simple fact that EVERY new card has driver issues at the start???
     

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